1. Field of the Invention
The invention concerns a unilaterally alternating backlash torque lock for mechanical control elements, couplings and the like, particularly for the steering gear of directly steered vehicles, such as fork lifts, industrial floor vehicles, etc., comprising an actuating member, a control and braking member. More particularly, the invention relates to an improved braking member comprising two loop springs surrounding a control element in slightly prestressed arrangement. The loop springs are connected at their ends with a power transfer part (or controlled member) and resting with their outer surfaces in a loosely sliding arrangement against a sleeve which communicates with an actuating member and is fixedly mounted on a frame.
2. Background Art
In mechanical torque transmitting systems, wherein the part driving the control element is exposed by backlash by the part being controlled, so-called laterally acting or unilaterally alternating torque locks are used. Torque locks of this type serve in fork lifts, equipped with direct ratio steering gears to brake back-lashing torque impacts caused by roughness of the road or other obstacles. As an example, impacts occurring at the steered wheels are transmitted by means of the steering column directly back to the direct steering means used in these vehicles and may attain strengths capable of inflicting severe injuries to hands, even in the case of low impact velocities. In steering brakes necessary for this type of utility, a loop spring often acts as the effective braking part. It is arranged between the outer part of the hub connected with the steering column as the actuating member and the inner part of the hub fastened to the steering column tube and acting as the brake drum. The inner part of the hub is also fixedly attached to a frame member.
In a known steering brake of this type, a single part loop spring is provided as the effective brake part. The spring is equipped for the purpose of fastening it to the outer part of the hub with a recessed groove each in its center area and its ends, and a pivot which is securely attached to the flange of the outer part of the hub surrounded by the spring engaging each of the grooves. This known steering brake has certain severe disadvantages. One disadvantage is that partial embossing of the loop spring is required for the formation of the grooves and represents an undesirable weakening of the spring, particularly since the groove located in the center area may be applied only by means of highly complex and thus expensive equipment. Another substantial disadvantage consists in the fact that the axial mounting of the loop springs onto the power transmission part is effected over a protruding driving pin secured to the power transmission part requiring extensive spreading of the spring during the mounting operation. This makes it necessary to use a spring material soft enough to permit such spreading. A spring of such low coiling strength then augments the disadvantage of the reduction in cross section resulting from the application of a groove in the spring.